The present invention generally pertains to data processing and is particularly directed to a scheme for simultaneously conveying both analog and digital information in a common digital signal.
It is desired to provide a simple, inexpensive scheme for communicating information from a given number of analog information input channels simultaneously with information from a given number of digital information input channels. Pulse width modulation (PWM) systems may be used for communicating both digital and analog information in a common digital signal. However, with a prior art PWM system, upon demodulation it is necessary to compare the duration of the receiver pulses with a reference pulse of a predetermined width. The implementation of this comparison of duration involves a significant amount of circuitry. In addition, this system requires calibration of the reference pulse in the demodulation section of the receiver in relation to the respective range of pulse widths provided by the modulation section of the transmitter. These drawbacks are significant in cost-sensitive applications.
One such application where expense is an important consideration is in the toy industry. And, a principal intended use of the present invention is for remotely controlling toys such as cars, robots, trains and model airplanes, wherein the analog information is communicated for providing proportional control and the digital information is communicated for providing on/off control.
Multiplexing schemes can also be used for simultaneously communicating both digital and analog information in a common digital signal. However, communications systems incorporating multiplexing also are too complicated and expensive for low-cost toy applications.
When a digital signal containing only digital information is to be decoded, typically tone decoders for detecting different audio frequency tones are used. However, these decoders also require calibration, and either include bulky capacitors and inductors, operational amplifiers, or phase-locked loops, which dissuade their use in low-cost toy application, where size and cost are principal considerations.